1. Field of the Invention
The invention relates to a process for the production of a polymer/metal or polymer/semiconductor composite of improved adhesive strength having an adhesive layer between polymer and metal or between polymer and semiconductor.
2. Description of Related Art
Due to their specific properties (for example low weight, good chemical resistance, high impact strength), polymeric materials are of considerable importance as work materials. Their excellent properties during processing by injection molding, casting, blow molding, extrusion, compression molding, etc., enable the production of articles and moldings having any desired geometry in a simple and precise manner. However, in many areas of application, in particular where specific demands are made of the electrical or magnetic properties, of the thermal conductivity or of the mechanical properties of a component, the desired property profiles can only be satisfied by polymer/metal or polymer/semiconductor composites. Due to the great differences in material properties between metals and polymers (for example coefficient of thermal expansion and modulus of elasticity) and the low physical and chemical bonding forces, the polymer/metal interface is a major weakness of these composites.
Various processes have already been disclosed for improving the adhesive strength in the polymer/metal composites (cf., for example, E. Sacher, J.-J. Pireaux, S. P. Kowalczyk, Metallization of Polymers, ACS Symposium Series 440, 1990; K. L. Mittal, J. R. Susko, Metallized Plastics 1, Plenum), namely a roughening of the polymer or of the metal layer by mechanical treatment, roughening of the polymer or of the metal layer by chemical etching (for example using a chromic/sulfuric acid mixture), roughening of the polymer or of the metal layer by physical etching (for example plasma etching), the introduction of chemical adhesion groups (for example O-containing functional groups) and deposition of intermediate layers (for example Sn, Cr, etc.).
EP-A-152 634 describes a process for the production of printed circuit boards in which metallic intermediate layers, in particular made from Cu, Ni, Ag, Zn, Al or alloys of these elements, are produced by vapor deposition or currentless deposition/electroplating, and the surfaces of these are subsequently roughened.
EP-A-237 114 describes a process for the production of an electroconductive adhesive bond in which the adhesion-promotion layer comprises transition metals from the series consisting of (I) Ti, V, Cr, Mn, Fe, Co, Ni and Cu and/or (II) Zr, Nb, Mo, Te, Ru, Rh, Pd and Ag, and is produced by electrochemical deposition or by sputtering.
These known processes have the disadvantages that the adhesion-promoting action is limited (only weak mechanical anchoring) and the areas of application of the polymer/metal composites is therefore limited.